The present invention relates to a set of weighing scales and aims more particularly at improving the guidance device of its movable portion relative to its fixed portion, the weight indicating device and the elastic device.
It aims at these two devices reducing friction to a minimum so that the elastic balancing device which measures the load is not disturbed by interfering phenomena. Consequently it improves the position and sensitivity of the weighing scales. Furthermore, the recommended constructional features lead to easy and economic manufacture within the framework of a mass production programme.
According to the invention the guidance device comprises at least three trains of rollers extending in radial planes passing through the guidance axis, whereby each roller idles about a rotation shaft which is orthogonal to the said guidance axis and being carried by one of the parts in such a way that between its tread and the other part there is a clearance sufficient so that contact with the latter can never occur with the complete system of rollers; wherein this guidance device cooperates with at least one anti-gyratory roller extending in a plane parallel to the guidance axis and which idles about a rotation shaft perpendicular to the said guidance axis carried by one of the parts and positioned with a clearance between two vertical elements of the other part; wherein the elastic device extends in accordance with the symmetrical guidance axis of the fixed part; wherein the indicating device placed between the fixed part and the moving part is of the floating type so that it is insensitive to the above-mentioned clearances and thereby transmits no opposing force to the elastic balancing device.
According to a particularly advantageous embodiment each guidance train comprises two rollers mounted loosely in terminal fork arms of an intermediate support comprising identical metal plates in the shape of the Greek letter omega and having straight branches, whereby these two plates are joined to one another by their median web and are fixed to one another and to the base of a positioning slot defined by a U-shaped member which projects radially over the part of the weighing scales to be equipped.
The anti-gyratory roller is mounted loosely in an intermediate cage comprising two identical omega-shaped metal plates having straight branches, whereby said two plates are joined by the extreme branches and are fixed to one another and to the base of a positioning slot defined by members projecting over that part of the weighing scales to be equipped.
The guidance roller trains are mounted on the outside of a sleeve of the movable part covering a passage or shaft in the fixed part, whereby the upper rollers pass through ports in this sleeve and all the rollers are able to come into contact with a cylindrical surface of the passage concentric to the guidance axis.